Trig4
From Exampleproblems
If a 10 foot tall ladder leans against a wall, and the base of the ladder is 5 feet away from the wall, how far up the wall does the ladder go?
Use Pythagoras' Theorem 
so that 
.
Then 
Remember that the square root gives a positive and negative answer, but since we're talking about a distance in the real world, use the positive answer.
